反向单链表Java [英] Reverse Singly Linked List Java

问题描述

有人可以告诉我为什么我的代码有效吗？我想要反转java中的单个链表：这是方法（无法正常工作）

Can someone tell me why my code dosent work? I want to reverse a single linked list in java: This is the method (that doesnt work correctly)

public void reverseList(){
    Node before = null;
    Node tmp = head;
    Node next = tmp.next;
    while(tmp != null){
      if(next == null)
         return;
      tmp.next = before;
      before = tmp;
      tmp = next;
      next = next.next;
    }
}

这是Node类：

public class Node{
   public int data;
   public Node next;
   public Node(int data, Node next){
      this.data = data;
      this.next = next;
   }
}

输入4-> 3-> 2-> 1我得到了输出4.我调试它并正确设置指针，但我仍然不明白为什么它只输出4。

On input 4->3->2->1 I got output 4. I debugged it and it sets pointers correctly but still I dont get why it outputs only 4.

推荐答案

Node next = tmp.next;
while(tmp != null){

那么当tmp == null时会发生什么？

So what happens when tmp == null?

你几乎得到了它。

Node before = null;
Node tmp = head;
while (tmp != null) {
    Node next = tmp.next;
    tmp.next = before;
    before = tmp;
    tmp = next;
}
head = before;

或更好（？）命名：

Node reversedPart = null;
Node current = head;
while (current != null) {
    Node next = current.next;
    current.next = reversedPart;
    reversedPart = current;
    current = next;
}
head = reversedPart;

ASCII art：

ASCII art:

        <__<__<__ __ : reversedPart    : head
                 (__)__ __ __
head :   current:      >  >  >

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